Field of the Technology
The invention relates to the field of optical coherence elastrography (OCE), specifically an OCE method under acoustic radiation force excitation using OCT Doppler variance and OCT correlation based techniques.
Description of the Prior Art
The process of elastrography is able to noninvasively image and measure the elastic properties of a soft tissue and has been used for medical diagnosis and tissue characterization. In the last decade, optical coherence tomography (OCT) has revealed the superiority of elastrography due to its high speed and high spatial resolution imaging. In an optical coherence elastrography (OCE) application, the OCT unit is used for detection of elastic vibration, and different mechanical excitation sources are employed to generate an elastic wave in the soft materials, including a focused air-puff device, an acoustic radiation force, a mechanical wave driver and a piezoelectric actuator. Since an acoustic radiation force (ARF) can generate elastic vibration inside the tissue without contact, it may be preferable for clinical diagnosis. ARF based OCE (ARF-OCE) has been employed to measure the shear wave and the longitudinal vibration. In previous shear wave detection using ARF-OCE methods, phase changes were detected by a Doppler OCT unit. The transducer and the OCT unit were located either on the same or opposing sides of the detected sample, and ARF induced axial displacement is parallel to the OCT detection beam.
However, there are many clinical cases, such as cornea imaging, where ARF excitation direction perpendicular or with at least a perpendicular component to the OCT beam is more convenient to implement. In addition, the phase changes may be distorted by bulk motion and phase wrapping, and high phase stability and subsequent data correction are required for phase-resolved OCT. Moreover, shear wave attenuation is rather large so the detectable range along its propagation direction is very limited